Devices for interior flushing of ship's tanks or similar are previously known from the publication EP 0 892 685. At the device according to this publication, one motor is used to rotate the rotatable part of a pipe for the supply of flushing liquid and another motor for rotating the flushing nozzle. Using two motors however, for rotating the rotatable part and the flushing nozzle, is an expensive and energy consuming solution which is sensitive to shutdowns.